Journal Article

Dose-dependent effect of dietary meat on endogenous colonic <i>N</i>-nitrosation

R. Hughes, A.J. Cross, J.R.A. Pollock and S. Bingham

in Carcinogenesis

Volume 22, issue 1, pages 199-202
Published in print January 2001 | ISSN: 0143-3334
Published online January 2001 | e-ISSN: 1460-2180 | DOI:
Dose-dependent effect of dietary meat on endogenous colonic N-nitrosation

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Human male volunteers were studied in a metabolic facility whilst they were fed randomized controlled diets. In eight volunteers there was a significant increase in faecal apparent total N-nitroso compounds (ATNC) and nitrite excretion (P < 0.0001 and P = 0.046, respectively) when randomized doses of meat were increased from 0 to 60, 240 and 420 g/day over 10 day periods. Mean (± SE) faecal ATNC levels were 54 ± 7 μg/day when the diets contained no meat, 52 ± 11 μg/day when the diets contained 60 g meat/day, 159 ± 33 μg/day with 240 g meat and 199 ± 36 μg/day with 420 g meat. Higher concentrations of NOC were associated with longer times of transit in the gut (r = 0.55, P = 0.001) and low faecal weight (r = –0.51, P = 0.004). There was no significant decline in levels in individuals fed 420 g meat for 40 days. The exposures found on the higher meat diets were comparable with other sources of N-nitroso compounds (NOC), such as tobacco smoke. Many NOC are known large bowel initiators and promotors in colon cancer, inducing G→A transitions in codons 12 and 13 of K-ras. Endogenous NOC formation, combined with prolonged transit times in the gut, may explain the epidemiological associations between high meat/low fibre diets and colorectal cancer risk.

Keywords: ATNC, apparent total N-nitroso compounds; MTT, mean transit time; NOC, N-nitroso compounds; PABA, p-aminobenzoic acid.

Journal Article.  3057 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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